Well, our good Defender Meredith Laver came up with this observation:
frequently, Ryouga and Ukyou bicker very much like Ranma and Akane. So,
she compiled a list of insults from the two, for each other. ^_^

Ukyou to Ryouga:

Aho! "Idiot!"

Boke! "Dummy!"

Ryouga no yatsu "Ryouga you jerk"

Houkou onchi! "You directionless idiot!"

Yarou! "Jerk!"

And, of course in the English dubs, there's "jackass", but
that's not reserved just for Ryouga. ^_^

Ryouga to Ukyou:

Baka! "Idiot!"

Temee, Kisama--Both of these a very informal and rude way to say
either "you!" or something like "Why you...!!"

Additional items:

An exchange from the second Ranma movie:
Ryouga to Ukyou: You got yourself into this "Lady"
Ukyou to Ryouga: Come and rescue me you "Pig-Headed Fool".
Contributed by AikoXOXO@aol.com

Another exchange from the same movie:
Ukyou to Ryouga: Why don't you PROVE you're a man and rescue me?
Ryouga to UkyouAhhh..sticks and stones.

As you may note, Ukyou's got a little bit more than Ryouga. But, if
you know of any more--for either one--please, do tell me. ^_^